Router with improved safety system

ABSTRACT

A router is described for cutting workpieces with router bits. The router includes a safety system configured to detect one or more dangerous conditions between a person and a router bit. The safety system includes a reaction subsystem configured to perform one or more predetermined actions in the event a dangerous condition is detected. In one embodiment, the safety system is configured to detect accidental contact between a person and the router bit, and then at least partially retract the router bit the person.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/197,975, filed Jul. 18, 2002, the disclosure ofwhich is herein incorporated by reference.

[0002] This application claims the benefit of and priority from U.S.Provisional Patent Application Serial No. 60/323,975, filed Sep. 21,2001, the disclosure of which is herein incorporated by reference.

FIELD OF THE INVENTION

[0003] The present invention relates to routers, and more particularlyto a router with a high-speed safety system.

BACKGROUND

[0004] Routers are a type of woodworking machinery used to cut wood,plastic and other materials. Routers typically include a generallycylindrical housing enclosing a motor, and a rotatable shaft or spindledriven by the motor and extending from one end of the housing. A varietyof router bits having different shapes are available and may be coupledto the shaft to perform different types of cuts. In some applications, arouter is mounted to a rear side of a workpiece support surface so thatthe router bit extends through a hole in the support surface. A userthen places a workpiece on the support surface and slides the workpieceagainst the router bit to cut the workpiece. In other applications, abase assembly is attached to the router to allow the router to be slidover the top of a workpiece. The router bit extends through a hole inthe base assembly to cut the underlying workpiece. Routers present arisk of injury to users because the spinning router bit is usuallyexposed during use. Thus, any contact between a user's body and thespinning router bit can cause serious injury.

[0005] The present invention provides a router with an improved safetysystem that is adapted to detect the occurrence of one or moredangerous, or triggering, conditions during use of the router, such aswhen a user's body contacts the spinning router bit. When such acondition occurs, the safety system is actuated to limit or even preventinjury to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a schematic block diagram of a router with a fast-actingsafety system according to the present invention.

[0007]FIG. 2 is a schematic diagram of an exemplary safety systemconfigured to stop the rotation of the router bit.

[0008]FIG. 3 is a schematic side elevation and partial cross-sectionalview of a router with a safety system according to the presentinvention.

[0009]FIG. 4 is a close-up schematic side elevation of an alternativereleasable coupling mechanism.

[0010]FIG. 5 is a close-up schematic side elevation of anotheralternative releasable coupling mechanism.

[0011]FIG. 6 is a schematic side elevation and partial cross-sectionalview of a router with an alternative safety system according to thepresent invention.

[0012]FIG. 7 is a schematic side elevation and partial cross-sectionalview of a router with another alternative safety system according to thepresent invention.

[0013]FIG. 8 is a partial schematic view showing an exemplary brake pawland brake engagement structure.

[0014]FIG. 9 is a partial schematic view showing an alternative brakepawl and brake engagement structure.

[0015]FIG. 10 is a partial schematic view showing another alternativebrake pawl and brake engagement structure.

[0016]FIG. 11 is a partial schematic view showing another alternativebrake pawl and brake engagement structure.

[0017]FIG. 12 is a partial schematic view showing another alternativebrake pawl and brake engagement structure.

[0018]FIG. 13 is a partial schematic view showing another alternativebrake pawl and brake engagement structure.

[0019]FIG. 14 is a schematic side elevation and partial cross-sectionalview of a router with an alternative safety system according to thepresent invention.

[0020]FIG. 15 is a schematic side elevation and partial cross-sectionalview of the router of FIG. 14 in which the spindle assembly has begun toretract.

[0021]FIG. 16 is a schematic side elevation and partial cross-sectionalview of the router of FIG. 14 in which the spindle assembly has fullyretracted.

[0022]FIG. 17 is a schematic side elevation and partial cross-sectionalview of a router with another alternative safety system according to thepresent invention.

[0023]FIG. 18 is a schematic side elevation and partial cross-sectionalview of a router with another alternative safety system according to thepresent invention.

[0024]FIG. 19 is a schematic side elevation and partial cross-sectionalview of the router of FIG. 18 in which the spindle assembly has fullyretracted.

[0025]FIG. 20 is a schematic side elevation of the cartridge of FIG. 18.

[0026]FIG. 21 is a schematic top plan view of the cartridge of FIG. 20.

DETAILED DESCRIPTION

[0027] A router according to the present invention is shownschematically in FIG. 1 and indicated generally at 10. Router 10 may beany of a variety of different types and configurations of router adaptedfor cutting workpieces, such as wood, plastic, etc. Router 10 includesan operative structure 12 having a cutting tool 14 and a motor assembly16 adapted to drive the cutting tool. Router 10 also includes a safetysystem 18 configured to minimize the potential of a serious injury to aperson using router 10. Safety system 18 is adapted to detect theoccurrence of one or more dangerous, or triggering, conditions duringuse of router 10. If such a dangerous condition is detected, safetysystem 18 is adapted to engage operative structure 12 to limit anyinjury to the user caused by the dangerous condition.

[0028] Router 10 also includes a suitable power source 20 to providepower to operative structure 12 and safety system 18. Power source 20may be an external power source such as line current, or an internalpower source such as a battery. Alternatively, power source 20 mayinclude a combination of both external and internal power sources.Furthermore, power source 20 may include two or more separate powersources, each adapted to power different portions of router 10.

[0029] It will be appreciated that operative structure 12 may take anyone of many different forms, depending on the type of router 10. As willbe described in more detail below, operative structure 12 typicallytakes the form of a rotatable shaft configured to couple cutting tool 14to motor assembly 16. The motor assembly includes one or more motorsadapted to drive the cutting tool. The motors may be either directly orindirectly coupled to the cutting tool by operative structure 12.

[0030] Safety system 18 includes a detection subsystem 22, a reactionsubsystem 24 and a control subsystem 26. Control subsystem 26 may beadapted to receive inputs from a variety of sources including detectionsubsystem 22, reaction subsystem 24, operative structure 12 and motorassembly 16. The control subsystem may also include one or more sensorsadapted to monitor selected parameters of router 10. In addition,control subsystem 26 typically includes one or more instruments operableby a user to control the router. The control subsystem is configured tocontrol router 10 in response to the inputs it receives.

[0031] Detection subsystem 22 is configured to detect one or moredangerous, or triggering, conditions during use of router 10. Forexample, the detection subsystem may be configured to detect that aportion of the user's body is dangerously close to, or in contact with,a portion of cutting tool 14. In some embodiments, detection subsystem22 may inform control subsystem 26 of the dangerous condition, whichthen activates reaction subsystem 24. In other embodiments, thedetection subsystem may be adapted to activate the reaction subsystemdirectly.

[0032] Once activated in response to a dangerous condition, reactionsubsystem 24 is configured to engage operative structure 12 quickly toprevent serious injury to the user. It will be appreciated that theparticular action to be taken by reaction subsystem 24 will varydepending on the type of router 10 and/or the dangerous condition thatis detected. For example, reaction subsystem 24 may be configured to doone or more of the following: stop the movement of cutting tool 14,disconnect motor assembly 16 from power source 20, place a barrierbetween the cutting tool and the user, retract the cutting tool from itsoperating position, etc. The reaction subsystem may be configured totake a combination of steps to protect the user from serious injury.Placement of a barrier between the cutting tool and teeth is describedin more detail in U.S. Provisional Patent Application Serial No.60/225,206, filed Aug. 14, 2000, the disclosure of which is hereinincorporated by reference. Retraction of the cutting tool from itsoperating position is described in more detail in U.S. ProvisionalPatent Application Serial No. 60/225,089, filed Aug. 14, 2000, thedisclosure of which is herein incorporated by reference.

[0033] The configuration of reaction subsystem 24 typically will varydepending on which action(s) are taken. In the exemplary embodimentdepicted in FIG. 1, reaction subsystem 24 is configured to stop themovement of cutting tool 14 and includes a brake mechanism 28, a biasingmechanism 30, a restraining mechanism 32, and a release mechanism 34.Brake mechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of router 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

[0034] It will be appreciated by those of skill in the art that theexemplary embodiment depicted in FIG. 1 and described above may beimplemented in a variety of ways depending on the type and configurationof operative structure 12. Turning attention to FIG. 2, one example ofthe many possible implementations of router 10 includes an operativestructure having a motor-driven spindle 42, and a generally circularbrake engagement structure 43 concentrically coupled to the spindle.During operation, any standard router bit (not shown) or other cuttingtool is also coupled to the spindle. As described in more detail below,brake mechanism 28 is adapted to engage brake engagement structure 43and stop the rotation of both the brake engagement structure and therouter bit. Alternatively, the brake engagement structure may beintegrally formed with the router bit to form a unitary element.

[0035] In the exemplary implementation, detection subsystem 22 isadapted to detect the dangerous condition of the user coming intocontact with the router bit. The detection subsystem includes a sensorassembly, such as contact detection plates 44 and 46, which arecapacitively coupled to the router bit to detect any contact between therouter bit and a user's body. Typically, the router bit, or some largerportion of operative structure 12, is electrically isolated from theremainder of router 10. Alternatively, detection subsystem 22 mayinclude a different sensor assembly configured to detect contact inother ways, such as optically, resistively, etc. In any event, thedetection subsystem is adapted to transmit a signal to control subsystem26 when contact between the user and the blade is detected. Variousexemplary embodiments and implementations of detection subsystem 22 aredescribed in more detail in U.S. Provisional Patent Application SerialNo. 60/225,200, filed Aug. 14, 2000, U.S. Provisional Patent ApplicationSerial No. 60/225,211, filed Aug. 14, 2000, U.S. Provisional PatentApplication Serial No. 60/270,011, filed Feb. 20, 2001, and U.S.Provisional Patent Application Serial No. 60/298,207, filed Jun. 13,2001, the disclosures of which are herein incorporated by reference.Alternatively, U.S. Provisional Patent Application Serial No.60/302,937, filed Jul. 2, 2001, the disclosure of which is hereinincorporated by reference, describes various embodiments of detectionsubsystem 22 configured to detect dangerous proximity between a personand the router bit.

[0036] Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of the router bit. Instruments48 may include start/stop switches, speed controls, direction controls,etc. Control subsystem 26 also includes a logic controller 50 connectedto receive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as router bit motion sensors,workpiece sensors, etc. In any event, the logic controller is configuredto control operative structure 12 in response to the user's inputsthrough instruments 48. However, upon receipt of a contact detectionsignal from detection subsystem 22, the logic controller overrides thecontrol inputs from the user and activates reaction subsystem 24 to stopthe motion of the router bit. Various exemplary embodiments andimplementations of control subsystem 26 are described in more detail inU.S. Provisional Patent Application Serial No. 60/225,059, filed Aug.14, 2000 and U.S. Provisional Patent Application Serial No. 60/225,094,filed Aug. 14, 2000, the disclosures of which are herein incorporated byreference.

[0037] In the exemplary implementation shown in FIG. 2, brake mechanism28 includes a brake pawl 60 mounted adjacent the edge of brakeengagement structure 43 and selectively moveable to engage and grip thebrake engagement structure. As will be described in more detail below,pawl 60 may be constructed of any suitable material adapted to engageand stop the brake engagement structure. It will be appreciated that theconstruction of pawl 60 will vary depending on the configuration ofbrake engagement structure 43. In any event, the pawl is urged againstthe brake engagement structure by a biasing mechanism such as a spring66. It should be understood that sliding or rotary movement of pawl 60may also be used. The spring is adapted to urge pawl 60 against thebrake engagement structure with sufficient force to grip the brakeengagement structure and quickly bring it to a stop, thereby stoppingthe rotation of the router bit.

[0038] The pawl is held away from the edge of the brake engagementstructure by a restraining mechanism such as a fusible member 70. Thefusible member is constructed of a suitable material adapted to restrainthe pawl against the bias of spring 66, and also adapted to melt under adetermined electrical current density. Examples of suitable materialsfor fusible member 70 include NiChrome wire, stainless steel wire, etc.The fusible member is connected between the pawl and a contact mount 72.Preferably, fusible member 70 holds the pawl relatively close to theedge of the brake engagement structure to reduce the distance pawl 60must travel to engage the brake engagement structure. Positioning thepawl relatively close to the edge of the brake engagement structurereduces the time required for the pawl to engage and stop the brakeengagement structure. Typically, the pawl is held approximately{fraction (1/32)}-inch to ¼-inch from the edge of the brake engagementstructure by fusible member 70; however, other spacings may also be usedwithin the scope of the invention.

[0039] Pawl 60 is released from its unactuated, or cocked, position toengage the router bit by a release mechanism in the form of a firingsubsystem 76. The firing subsystem is coupled to contact mount 72, andis configured to melt fusible member 70 by passing a surge of electricalcurrent through the fusible member. Firing subsystem 76 is coupled tologic controller 50 and activated by a signal from the logic controller.When the logic controller receives a contact detection signal fromdetection subsystem 22, the logic controller sends an activation signalto firing subsystem 76, which melts fusible member 70, thereby releasingthe pawl to stop the blade. Various exemplary embodiments andimplementations of reaction subsystem 24 are described in more detail inU.S. Provisional Patent Application Serial No. 60/225,056, filed Aug.14, 2000, U.S. Provisional Patent Application Serial No. 60/225,169,filed Aug. 14, 2000, and U.S. Provisional Patent Application Serial No.60/225,170, filed Aug. 14, 2000, the disclosures of which are hereinincorporated by reference.

[0040] In some embodiments, activation of the brake mechanism mayrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically are single-usecomponents which must be replaced before the safety system is ready tobe used again. Thus, it may be desirable to incorporate one or moreportions of safety system 18 in a cartridge that can be easily replaced.For example, in the exemplary implementation depicted in FIG. 2, safetysystem 18 includes a replaceable cartridge 80 having a housing 82. Pawl60, spring 66, fusible member 70 and contact mount 72 are all mountedwithin housing 82. Alternatively, other portions of safety system 18 maybe mounted within the housing. In any event, after the reaction systemhas been activated, the safety system can be reset by replacingcartridge 80. The portions of safety system 18 not mounted within thecartridge may be replaced separately or reused as appropriate. Variousexemplary embodiments and implementations of a safety system using areplaceable cartridge are described in more detail in U.S. ProvisionalPatent Application Serial No. 60/225,201, filed Aug. 14, 2000 and U.S.Provisional Patent Application Serial No. 60/225,212, filed Aug. 14,2000, the disclosures of which are herein incorporated by reference.

[0041] In the exemplary embodiment depicted in FIG. 2 and describedabove, brake mechanism 28 is configured to stop the rotation of thespindle and at least a portion of the motor assembly (e.g., armature,etc.) as well as the router bit. While this configuration has theadvantage of simplicity of design, it may require a larger brake pawl toabsorb the energy of the spinning spindle and motor armature which arerelatively heavy compared to the router bit. Thus, it may be desirableto decouple the router bit from the spindle and motor during braking.This may allow a smaller brake pawl to be used, and may reduce strain onthe motor assembly.

[0042] One exemplary configuration of router 10 in which the router bitmay be selectively uncoupled from the motor is depicted in FIG. 3.Router 10 includes a main housing 84 enclosing a motor assembly 16.Typically, housing 84 is generally cylindrical having generally circularsides 86 extending from a lower end 88 to an upper end (not shown).Alternatively, housing 84 may be any desired shape or configuration. Arotatable spindle 42 is coupled to the motor assembly and extendsthrough an opening in lower end 88. The motor assembly is adapted todrive the spindle at rotational speeds typically between 3,000 and30,000 rpm, although other speeds may also be used. Optionally, router10 may include a variable speed control to allow an operator to select adesired speed.

[0043] As shown in FIG. 3, router 10 is coupled to a base assembly 90adapted to stably support the router on a surface of a workpiece. Baseassembly 90 may be any of a variety of base assemblies such as are knownin the art. The base assembly typically includes a generally cylindricalshell 92 adapted to fit over, or otherwise couple to, housing 84adjacent the lower end. Shell 92 may be coupled to housing 84 using afriction fit coupling, or any other suitable mechanism such as screws,etc. The shell extends beyond the lower end to at least partiallyenclose spindle 42. Portions of shell 92 may be open or transparent toallow an operator to view the area of a workpiece being cut duringoperation. The axial position of shell 92 relative to housing 84typically is adjustable to allow the operator to select the distance thebase assembly extends beyond the lower end. Optionally, the baseassembly may include a support plate 94 mounted to the end of shell 92,and adapted to slide against the surface of a workpiece. Support plate94 includes an opening 96 which is generally axially aligned withspindle 42, and which is sized to allow the passage of a router bit 98.Base assembly 90 may also include one or more handle members 100 adaptedto be gripped by an operator to move the router over the workpiece.

[0044] As is well known to those of skill in the art, base assembly 90is typically used to allow an operator to slide the router over thesurface of a stationary workpiece while cutting material from a lateraledge of the workpiece. Alternatively, router 10 may be mounted to theunderside of a router table or similar support structure (not shown) sothat the router bit extends through a work surface adapted to support aworkpiece. In this latter configuration, the operator slides theworkpiece over the work surface and against the router bit to cut theworkpiece. It will be appreciated by those of skill in the art thatsafety system 18 may be used with router 10 regardless of whether therouter is coupled to base assembly 90 or a router table, etc.Furthermore, while one particular housing assembly has been describedabove, it will be appreciated that safety system 18 may be adapted asnecessary for use with any type of housing assembly.

[0045] In the exemplary implementation depicted in FIG. 3, router bit 98is coupled to spindle 42 through a releasable coupling assembly 102.Releasable coupling assembly 102 is adapted to couple the router bit tothe spindle in an axially-fixed and rotationally-fixed positionconcentric with the spindle. Thus, the motor assembly is indirectlycoupled to rotationally drive the router bit through spindle 42 andreleasable coupling assembly 102. During normal operation, thereleasable coupling assembly imparts the rotation of the spindle to therouter bit. However, during braking, the releasable coupling assembly isconfigured to rotationally uncouple the router bit from the motorassembly so that the router bit may be braked while the motor continuesto spin. In other words, releasable coupling assembly 102 is atorque-limiting coupling configured to at least temporarily uncouple therouter bit from the motor assembly in response to a high torque load onthe router bit and/or releasable coupling assembly. Releasable couplingassembly 102 typically is configured to retain the router bit axiallycoupled to the spindle or motor assembly to prevent the router bit fromleaving the spindle and possibly causing damage to the router or injuryto the operator.

[0046] It will be appreciated that releasable coupling assembly 102 maybe configured to rotationally uncouple the router bit in a variety ofdifferent ways such as are known to those of skill in the art. Forexample, the exemplary releasable coupling assembly depicted in FIG. 3includes a first or fixed section 104 and a second or releasable section106. First section 104 is rigidly coupled to the end of spindle 42 thatextends out of housing 84. First section 104 includes a cylindricalfitting or cap 108 with an open end threadedly mounted on spindle 42.The direction of the threaded coupling between the spindle and cap 108may be selected, relative to the rotational direction of the spindle, sothat the cap is self-tightening onto the spindle during operation.

[0047] Second section 106 is coupled to first section 104 through bothan axial coupling mechanism and a rotational coupling mechanism. Whilethe axial coupling mechanism is configured to hold second section 106securely to first section 104, the rotational coupling mechanism isconfigured to self-release under specified torque loads. Second section106 includes a brake engagement structure 43 and a router bit collet orchuck 110. Brake engagement structure 43 is generally disk-shaped with acentral bore on one end adapted to fit at least partially over cap 108.The opposing end of brake engagement structure 43 includes a recessadapted to receive a bolt 112, which extends through a hole in the brakeengagement structure to threadedly engage the closed end of cap 108.Thus, bolt 112 serves as the axial coupling mechanism to axially couplethe brake engagement structure 43 to cap 108. Alternatively, any othersuitable mechanism may be used to axially couple the brake engagementstructure to the cap.

[0048] As mentioned above, cap 108 has a generally cylindrical exteriorsurface allowing the brake engagement structure to rotate relative tocap 108. Thus, bolt 112 does not rotationally couple brake engagementstructure 43 to cap 108. Rather, the brake engagement structure isrotationally coupled to the cap by a releasable coupling member in theform of a shear pin 114. As shown in FIG. 3, shear pin 114 is positionedwithin aligned recess regions formed in the circular adjoining faces ofcap 108 and brake engagement structure 43. Thus, shear pin 114 impartsthe rotation of the cap to the brake engagement structure.Alternatively, a plurality of shear pins may be used to rotationallycouple the brake engagement structure to the cap. As a furtheralternative, other types of releasable coupling elements may be used.

[0049] As is well known to those of skill in the art, shear pin 114 is atorque-limiting coupling device that will shear off, or release, at apredetermined shearing force proportional to the torque between thebrake engagement structure and the cap. The amount of torque required toshear the shear pin will vary depending on the configuration of theshear pin (i.e., size, shape, material, hardness, etc.). Typically, theconfiguration of shear pin 114 is selected to ensure shearing only inresponse to a threshold torque corresponding to the engagement of abrake pawl or other braking component with the brake engagementstructure. Thus, shear pin 114 will not shear under normal operatingconditions. However, once the brake pawl engages the brake engagementstructure, shear pin 114 will shear, thereby releasing brake engagementstructure 43 to rotate freely about cap 108. This releases therotational coupling between the router bit and the motor assembly andspindle so that the rotation of the router bit can be stopped withoutstopping the motor and spindle.

[0050] While shear pin 114 has been described above as one example of areleasable, rotational coupling between the router bit and the spindleor motor, it will be appreciated that any of a variety of alternativemechanisms may be used. As another example, brake engagement structure43 and router bit 98 may be coupled to spindle 42 by a releasablecoupling that automatically re-couples the router bit to the spindleonce the torque load decreases to a predetermined level. One example ofsuch a coupling is illustrated in FIG. 4. As shown, brake engagementstructure 43 is coupled to cap 108 by a spring-loaded, torque-limitingcoupling assembly. The shank of bolt 112 passes through brake engagementstructure 43 to threadedly engage cap 108. A compression spring 116 isdisposed around the shank of the bolt between the brake engagementstructure and the head of the bolt. Spring 116 urges the brakeengagement structure and cap tightly together. A plurality of ballbearings 118 are disposed between the cap and brake engagementstructure, and normally sit in recesses in the surfaces of the cap andbrake engagement structure. Alternatively, the cap and/or the brakeengagement structure may have one or more circular tracks of alternatingridges and depressions which the ball bearings may be seated in.

[0051] During normal operation, the brake engagement structure isrotationally coupled to the cap by ball bearings 118, which are held inthe recesses by the compressive force exerted by spring 116. However,upon application of sufficient torque, ball bearings 118 will roll outof the recesses, allowing the brake engagement structure to rotaterelative to the cap. The amount of torque necessary to unseat the ballbearings (the “decoupling-torque threshold”) will depend on thecompressive force exerted by spring 116. Thus, spring 116 may beselected to yield a desired decoupling-torque threshold. Optionally,suitable alignment structure (not shown) may be disposed between thebrake engagement structure and cap to maintain the ball bearings in aconcentric path about bolt 112. In such case, the ball bearings wouldcontinually roll into and out of the recesses until the applied torquedecreased below a threshold level, at which point the ball bearingswould reseat into the recesses, thereby re-coupling the brake engagementstructure to the cap. It will be appreciated that the torque thresholdlevel at which the ball bearings will be unseated may be the same as, ordifferent than, the torque threshold level at which the unseated ballbearings will be reseated. While the exemplary releasable couplingdepicted in FIG. 3 may be less expensive to manufacture, the exemplarycoupling depicted in FIG. 4 has the advantage of not requiringreplacement of a shear component to return the router to normaloperation after the brake mechanism has been triggered to stop therouter bit.

[0052] The exemplary coupling depicted in FIG. 4 is a relatively simpleversion of a variety of torque-limiting couplers known in the art. Anyof these couplers may be used to releasably couple the router bit to thespindle and motor assembly. A few examples of the many such suitablecouplers, showing just a few of the possible configurations, aredescribed in the following U.S. patents, the disclosures of which areherein incorporated by reference: U.S. Pat. No. 4,898,249 to Ohmori,U.S. Pat. No. 5,738,469 to Hsu, U.S. Pat. No. 5,277,527 to Yokota, andU.S. Pat. No. 6,045,303 to Chung. Additionally, any other suitabletorque-limiting coupler such as are known in the art may be used.

[0053] Returning attention to FIG. 3, chuck 110 is axially androtationally coupled to brake engagement structure 43 by any suitablecoupler mechanism. In the exemplary implementation, chuck 110 and brakeengagement structure 43 are formed as an integral, unitary assembly.This ensures that the chuck and router bit remain securely coupled tothe brake engagement structure during braking. Alternatively, chuck 110may be coupled to brake engagement structure 43 by any known mechanismadapted to securely hold the chuck and brake engagement structuretogether during both operation and braking. For example, the exemplarybrake engagement structure depicted in FIG. 4 includes an externallythreaded ring 120 adapted to engage a matching threaded bore on chuck110. Optionally, the threaded bore on the chuck may be a different sizethan the threaded end of spindle 42 to prevent an operator frominadvertently attaching the chuck to the spindle without the brakeengagement structure. Alternatively, ring 120 may be internally threadedto receive a matching threaded post (not shown) on chuck 110. As will bedescribed in more detail below, either chuck 110 or brake engagementstructure 43 may include a locking mechanism to prevent inadvertentloosening during operation or braking.

[0054] Chuck 110 may be any suitable router chuck configured to securelyhold router bit 98 during both normal operation and during braking. Inthe exemplary implementation, chuck 110 is a quick-release router chucksuch as is available from Jacobs of Clemson, S.C. under the designationHAND-TITE, POWERCOLLET, router chuck. Other suitable chucks aredescribed in the following U.S. patents, the disclosures of which areherein incorporated by reference: U.S. Pat. No. 5,755,448 to Kanaan etal., U.S. Pat. No. 5,820,136 to Han et al., U.S. Pat. No. 5,921,563 toHuggins et al., and U.S. Pat. No. 5,947,484 to Huggins et al.

[0055]FIG. 5 illustrates an alternative mechanism for coupling routerbit 98 to brake engagement structure 43. As shown, brake engagementstructure 43 is formed to define a collet 122 adapted to receive routerbit 98. A collet nut 124 threadedly engages the outer surface of collet122 to tighten the collet around the router bit as is well known in theart. However, depending on the direction of the threads on collet 122,collet nut 124 may tend to self-loosen either during normal operation orduring braking. Therefore, the coupling mechanism also includes aspring-loaded locking member 126 disposed around the collet, and adaptedto extend at least partially around the sides of collet nut 124. Thelocking member includes a projecting key (not shown) adapted to slidealong an axial channel 128 in collet 122. Thus, the locking member isrotationally fixed to the collet. A compression spring 130 is positionedaround the collet between the brake engagement structure and the lockingmember to bias the member toward collet nut 124. Locking member 126includes an internal bore shaped to correspond to, and fit around, theexternal shape of the nut (e.g., hexagonal, octagonal, etc.). As aresult, when locking member 126 is slid over collet nut 124, the colletnut is prevented from rotating relative to brake engagement structure43. The locking member may be pressed away from the collet nut againstthe bias of spring 130 to tighten or loosen the collet nut on thecollet. Alternatively, it will be appreciated that a variety of otherlocking mechanisms may be used to prevent collet nut 124 fromself-loosening about collet 122.

[0056] As described above and in the incorporated references, safetysystem 18 includes a detection subsystem configured to detect one ormore dangerous conditions such as contact between a person and therouter bit, hazardous proximity of a person to the router bit, etc.Typically, router bit 98 is electrically insulated from motor assembly16 and housing 84. It will be appreciated that the router bit may beelectrically insulated in any of a variety of different ways. Variousexemplary configurations and mechanisms for electrically insulating thecutting tool from the remainder of the machine are described in theincorporated references. As any of these configurations and mechanismsmay be adapted for use with router 10, additional description will notbe provided here. Likewise, various suitable configurations andmechanisms for monitoring the router bit and detecting contact,proximity, etc., are described in the incorporated references and,therefore, will not be described further herein. It will be understoodthat safety system 18 may incorporate any one or combination of thevarious alternative embodiments described in the references incorporatedabove.

[0057] Returning attention to FIG. 3, safety system 18 also includes areaction subsystem 24 configured to stop the rotation of the router bitin the event the dangerous condition is detected. The reaction subsystemmay be configured in any of a number of different ways. A variety ofdifferent exemplary reaction subsystems are described in the referencesincorporated herein, and may be adapted for use with router 10.Alternatively, FIG. 3 illustrates another exemplary embodiment in whichreaction subsystem 24 includes at least one brake mechanism 28 having abrake pawl adapted to engage the brake engagement structure and stop therotation of the brake engagement structure and router bit. Whileexemplary reaction subsystem 24 is described as having a single brakemechanism, it will be appreciated that the reaction subsystem mayalternatively have a plurality of similar or different brake mechanismsas illustrated in FIG. 3.

[0058] Exemplary brake mechanism 28 includes a brake pawl 60 adapted toengage brake engagement structure 43 and stop the rotation of the brakeengagement structure. Brake pawl 60 is biased to move into contact withand engage brake engagement structure 43 by a suitable biasing mechanismsuch as spring 66. The brake pawl is held spaced-apart from the brakeengagement structure by a suitable restraining mechanism, such as afusible member (not shown). A suitable release mechanism, such as afiring subsystem (not shown) is adapted to release the brake pawl fromthe restraining mechanism to move into contact with the brake engagementstructure under the urging of spring 66. A variety of differentexemplary brake mechanisms, biasing mechanisms, restraining mechanisms,and release mechanisms are described in the references incorporatedherein. In addition, alternative actuators suitable for moving brakepawl 60 into contact with brake engagement structure 43 are described inU.S. Provisional Patent Application Serial No. 60/302,916, filed Jul. 3,2001, the disclosure of which is herein incorporated by reference.

[0059] Brake pawl 60 is positioned adjacent the brake engagementstructure to engage the edge of the brake engagement structure. In theexemplary embodiment, brake pawl 60 is mounted in a replaceablecartridge 80. A variety of alternative embodiments of cartridge 80 aredescribed in the incorporated references. The cartridge is removablycoupled to housing 84 to support the cartridge and brake pawl duringbraking. A portion 132 of cartridge 80 may be adapted to be receivedinto a matching receptacle or socket in housing 84 to support thecartridge and electrically couple the cartridge to detection subsystem22 and/or control subsystem 26. Control subsystem 26 may be configuredto prevent operation of the router unless cartridge 80 is properlyreceived in the socket. The cartridge is sized to ensure the brake pawlis aligned with the brake engagement structure when the cartridge isreceived in the socket. Optionally, safety system 18 may include aspacing detection system adapted to determine whether the brake pawl isat an acceptable spacing from the brake engagement structure, and toprevent operation of the router unless the brake pawl is properly spacedfrom the brake engagement structure.

[0060] Alternatively, cartridge 80 may be coupled to base assembly 90instead of, or in addition to, housing 84. For example, in the exemplaryembodiment illustrated in FIG. 6, a portion 134 of the cartridge isadapted to be received within a channel 136 of shell 92. The baseassembly holds the cartridge securely during normal operation andbraking. A portion 138 of the cartridge may be adapted to engage amatching receptacle or socket in the router to electrically couple thecartridge to the detection subsystem and/or control subsystem. A biasingmechanism such as a spring 140 may be disposed in channel 136 to holdthe cartridge against lower end 88 as the axial position of the baseassembly is adjusted relative to housing 84. It will be appreciated thatcartridge 80 may be coupled to the router housing and/or the baseassembly by any other suitable coupling mechanism such as screws, clips,etc.

[0061] In some embodiments of safety system 18, brake pawl 60 and/oranother component of the reaction subsystem may be a single-usecomponent. Thus, in the event the brake mechanism is actuated to stopthe router bit, the used cartridge is removed and a new cartridge isinstalled to place the router back in service. Alternatively, thesingle-use component within the cartridge may be replaced and thecartridge reinstalled. Brake engagement structure 43 may be either asingle-use component or it may be reusable one or more times.

[0062] In the embodiments depicted in FIGS. 3-6, brake engagementstructure 43 is positioned externally to housing 84. However, it will beappreciated that the brake engagement structure may alternatively bepositioned within the housing. For example, FIG. 7 illustrates anembodiment in which brake engagement structure 43 is positioned withinhousing 84 adjacent lower end 88. One advantage of this configuration isthat the rotating brake engagement structure and the brake pawl are notexposed outside of housing 84.

[0063] As shown in FIG. 7, brake engagement structure 43 is coupled tospindle 42 at a point inside housing 84 by a releasable coupling 142.The releasable coupling may be any suitable releasable coupling such asthe torque-limiting couplings described above, or other releasablecouplings known in the art. Alternatively, spindle 42 may include atorque-limiting mechanism adapted to uncouple a portion of the spindleproximate the brake engagement structure from the remainder of thespindle and motor assembly. As a further alternative, brake engagementstructure 43 may be rigidly coupled to the spindle and brake mechanism28 may be configured to stop the rotation of the spindle and motorarmature. In the latter case, brake engagement structure 43 may bepositioned at any point on spindle 42 including the opposite end ofrouter 10 or a position between the opposing ends.

[0064] In any event, brake pawl 60 is configured to engage brakeengagement structure 43 within housing 84. In the exemplary embodiment,cartridge 80 is adapted to be received into a matching socket orreceptacle in housing 84 to position the brake pawl adjacent the edge ofthe brake engagement structure. Thus, the cartridge is securelysupported by the housing and electrically coupled to the detectionsubsystem and/or the control subsystem. Optionally, the cartridge may beshaped to match the shape and contours of housing 84, thereby forming aportion of the exterior surface of the router housing when properlyinstalled. Preferably, though not necessarily, the cartridge isconfigured to extend flush with, or behind, lower end 88 of housing 84to allow the router to be mounted to a workpiece support surface (e.g.,router table, etc.) without interference.

[0065] A portion 144 of brake engagement structure 43 extends through ahole in lower end 88 to couple to router chuck 110. Alternatively, aportion of the router chuck may extend through lower end 88 into housing84 to couple to the brake engagement structure. In any event, chuck 110is axially and rotationally coupled to the brake engagement structure tosecurely hold the router bit during both operation and braking. Chuck110 may be coupled to brake engagement structure 43 by any suitablecoupling mechanism such as described above. Similarly, chuck 110 may beany suitable router bit chuck or collet such as described above.

[0066] Optionally, brake engagement structure 43 may be configured toforce air backward into housing 84, thereby eliminating the need (ifany) for a separate air-cooling fan. For example, in the exemplaryembodiment depicted in FIG. 7, brake engagement structure 43 includesone or more airflow channels 146 adapted to push air into housing 84when the brake engagement structure is rotating. Thus, brake engagementstructure 43 functions as the cooling fan for motor assembly 16 (i.e.,the cooling fan is the brake engagement structure). It will beappreciated that airflow channels 146 may be sized and shaped as neededto achieve a desired airflow. In the depicted embodiment, airflowchannels 146 are disposed inside the outer perimeter of brake engagementstructure 43. However, it will be appreciated that the airflow channelsmay alternatively extend out to the perimeter of the brake engagementstructure. Typically, airflow channels 146 will be configured andarranged to maintain the brake engagement structure in a balancedcondition for smooth rotation.

[0067] As described above, brake mechanism 28 includes one or morebraking components adapted to engage and stop brake engagement structure43 and router bit 98. It will be appreciated that the particularconfiguration of the braking component will vary depending on theconfiguration of the brake engagement structure, and that variouscombinations of the braking component and brake engagement structure maybe used. Typically, the braking component and the brake engagementstructure are configured to ensure the brake mechanism stops therotation of the brake engagement structure and router bit within adesired time period (“braking time”) after the dangerous condition isdetected. The desired braking time may vary depending on the type ofdangerous condition detected. For example, if the dangerous condition iscontact between a person and the router bit, then a relatively shortbraking time is usually desirable to minimize any injury to the person.However, if the dangerous condition is proximity between the person andthe router bit, then a somewhat longer braking time may be sufficient toprevent or minimize injury. Where contact is the dangerous conditiondetected, the brake engagement structure and braking component arepreferably configured to achieve a braking time of approximately10-milliseconds, and more preferably approximately 5-milliseconds. Whereproximity is the dangerous condition being detected, the preferredbraking time will depend on the distance between the person and therouter bit at which proximity is detected. For instance, if proximity isdetected when a part of the person's body is ⅛-inch from the router bit,then the braking time may be longer than if proximity is detected at aspacing of {fraction (1/32)}-inch.

[0068] In some embodiments brake pawl 60 and/or brake engagementstructure 43 may include structure adapted to increase the grip orbinding of the brake pawl and brake engagement structure. For example,the references incorporated herein describe many different alternativeconfigurations of brake pawl 60 which may be suitable for engaging andstopping brake engagement structure 43. Many of the brake pawlconfigurations described in those references are adapted to engage andbind against a circular blade having a plurality of teeth disposedaround the perimeter of the blade. The blade is usually constructed of ametal such as steel, while the brake pawl is constructed of a softermaterial which allows the teeth to cut into and wedge onto the brakepawl. Typical brake pawl materials include relatively high strengththermoplastics such as polycarbonate, ultrahigh molecular weightpolyethylene (UHMW) or Acrylonitrile Butadiene Styrene (ABS), etc., ormetals such as aluminum, etc. It will be understood that the term “brakepawl” is used herein generically to mean a braking component of anysize, shape or configuration.

[0069] In the exemplary embodiment, depicted in FIG. 8, brake engagementstructure 43 includes a plurality of gripping elements 148, which aresimilar to saw teeth. The brake pawl is biased by spring 66 to pivotinto contact with the edge of the brake engagement structure so thatgripping elements 148 engage the brake pawl. The brake engagementstructure is constructed of a material having a greater hardness thanthe material of the brake pawl so that the gripping elements at leastpartially “bite” into brake pawl 60. Constructing the brake engagementstructure from a material that is relatively durable and harder than thebrake pawl material ensures that the brake engagement structure usuallywill not be damaged during braking. The exemplary brake pawl is sizedand configured to ensure that the brake pawl does not pivot past thebrake engagement structure without binding against the brake engagementstructure and stopping its rotation.

[0070] While one particular brake pawl shape is depicted, many differentvariations and modifications may be used. Additionally, it will beappreciated that the exact size and shape of gripping elements 148 isnot critical, but instead may vary with the particular brake pawl. FIGS.9 and 10 show just a few examples of alternative brake pawl shapesadapted to grip the brake engagement structure. The exemplary brake pawldepicted in FIG. 9 is shaped to generally conform to the perimeter ofthe brake engagement structure, thereby providing greater contact areabetween the brake pawl and brake engagement structure. The exemplarybrake pawl depicted in FIG. 10 is shaped to form a cam wedge relative tothe brake engagement structure to quickly bind against the brakeengagement structure. Additionally, the alternative brake pawlsdescribed in the incorporated references may also be used to stop therotation of the toothed brake engagement structure depicted in FIG. 8.

[0071] While the brake engagement structure described above is adaptedto bite into the brake pawl, safety system 18 may alternatively beconfigured so that the brake component bites into the brake engagementstructure to increase the binding action between the brake pawl andbrake engagement structure. For example, FIG. 11 illustrates anembodiment in which brake pawl 60 includes one or more gripping elements150 adapted to bite into brake engagement structure 43. In thisembodiment, the brake pawl typically is constructed of a material havinga greater hardness than the material of the brake engagement structure.For example, the brake pawl may be constructed of steel to engage aplastic or aluminum brake engagement structure, etc.

[0072]FIG. 12 illustrates another alternative embodiment in which brakepawl 60 includes at least one latching element 152 and at least onebinding element 154. Latching element 152 is adapted to quickly contactand latch on to the rotating brake engagement structure, therebyimparting the energy of the brake engagement structure to the brakepawl. The speed and energy of the brake engagement structure istransferred to the brake pawl, causing the brake pawl to quickly pivotfurther into contact with the edge of the brake engagement structure.Thus, as illustrated in FIG. 12, the latching element ensures that thebinding element is driven into the edge of the brake engagementstructure to wedge in the brake engagement structure and quickly stopits rotation. While the edge of the brake engagement structure isillustrated as being smooth, it will be appreciated that the edge of thebrake engagement structure may alternatively include gripping structuresuch as ridges, etc., adapted to prevent latching element 152 or bindingelement 154 from sliding around the edge of the brake engagementstructure.

[0073] Brake pawl 60 and/or brake engagement structure 43 may also beshaped to increase the gripping action between the components insteadof, or in addition to, other grip-enhancing structures. For example,FIG. 13 shows a cross-sectional view of an alternative brake engagementstructure shaped to wedge within a channel 156 formed in the contactingsurface of the brake pawl. As can be seen, channel 156 is tapered to awidth that is less than the width of the brake engagement structure sothat the upper and lower surfaces of the brake engagement structure willwedge against the upper and lower surfaces of the channel. It will beappreciated that channel 156 may be plural channels and/or may have anyof a variety of shapes to match corresponding brake engagementstructures. Alternatively, the brake pawl may be shaped to wedge withinone or more channels formed in the brake engagement structure.

[0074] As described above and in the incorporated references, reactionsubsystem 24 may be adapted to retract a cutting tool away from itsoperating position (and therefore the user) upon the detection of adangerous condition. The reaction subsystem may be configured to retractthe cutting tool in addition to, or instead of, stopping the movement ofthe cutting tool. Thus, the reaction subsystem may be configured toretract router bit 98 at least partially away from its operatingposition upon detection of a dangerous condition such as accidentalcontact between a user and the router bit. Optionally, the reactionsubsystem may be configured also to quickly stop the movement of therouter bit simultaneous, or substantially simultaneous, with retractingthe router bit.

[0075] It will be appreciated that reaction subsystem 24 may beconfigured in any of a variety of different ways to at least partiallyretract the router bit from its fully-extended or operative position. Asone example, FIGS. 14-16 illustrate an exemplary embodiment of router 10and safety system 18 in which the router bit is retracted at leastpartially toward housing 84. As shown, router bit 98 is axially androtationally coupled to a retractable spindle assembly 160 by a chuck110 or other suitable coupling mechanism. Retractable spindle assembly160 is coupled to a shaft 162 that forms part of the motor armature (notshown) by a coupling mechanism 164 adapted to allow the spindle assemblyto move axially relative to housing 84. In the exemplary embodiment,coupling mechanism 164 is integral with shaft 162 to form the end of theshaft proximate spindle assembly 160. Coupling mechanism 164 defines ahollow, cylindrical chamber 166 with a tapered end. The end 168 ofspindle assembly 160 proximate the coupling mechanism is disposed withinchamber 166 and outwardly tapered to conform to the tapered end of thechamber. A portion of the coupling mechanism may be removably connected(e.g., by screws, clips, etc.) from the remainder of the couplingmechanism to facilitate installation of end 168 within chamber 166.Alternatively, chamber 166 may be formed on the end of spindle assembly160 to receive the end of shaft 162. As a further alternative, chamber166 may be replaced by a separate sleeve or other coupler adapted torotationally connect the end of shaft 162 to end 168 of the spindleassembly.

[0076] In the exemplary embodiment, the tapered end of chamber 166 andspindle end 168 are formed with complementary gripping structures 170such as flutes, teeth or grooves so that rotation of shaft 162 istranslated to spindle assembly 160 by flutes 170. Alternatively, chamber166 and end 168 may be formed with other rotational gripping structure.In addition, while chamber 166 and end 168 are illustrated as havinggenerally conically-tapered shapes, other shapes may alternatively beused such as round, etc. In any event, exemplary coupling mechanism 164is configured to rotationally couple spindle assembly 160 to shaft 162when end 168 is seated within the tapered end of chamber 166. However,end 168 is axially movable within chamber 166 as illustrated in FIGS. 15and 16. When spindle assembly 160 retracts, flutes 170 on chamber 166and end 168 disengage, thereby releasing the rotational coupling betweenthe spindle assembly and shaft 162. Alternatively, chamber 166 and end168 may be shaped to maintain a rotational coupling as the spindleassembly slides axially relative to the shaft.

[0077] Retractable spindle assembly 160 is supported within housing 84by a retractable bearing assembly 172 configured to slide axially withinthe housing. Retractable bearing assembly 172 includes a collar 174adapted to receive a pair of bearings 176. The bearings are seatedwithin a hollow central bore of collar 174 and maintained insubstantially parallel alignment to receive and rotationally support thecentral portion 178 of spindle assembly 160. Central portion 178 mayinclude one or more integral or removable clips or shoulder structures180 adapted to prevent the spindle assembly from sliding out of positionwithin bearings 176.

[0078] Retractable bearing assembly 172 is slidably received within acentral bore 182 of housing 84. The exterior corner of collar 174adjacent housing lower end 88 and the interior corner of bore 182 aretapered so that the collar is self-seating and self-aligning within thecentral bore when the collar is in its unretracted position as shown inFIG. 14. A guide ring 184 extends outward from collar 174 to contact andslide against the interior wall of central bore 182. Guide ring 184maintains collar 174 and spindle assembly 160 centrally aligned withinhousing 84 as the collar and spindle assembly move axially relative tothe housing.

[0079] Retractable bearing assembly 172 also includes a biasingmechanism 186 configured to urge collar 174 toward lower end 88 ofhousing 84. In the exemplary embodiment, biasing mechanism 186 takes theform of a spiral compression spring sized to fit around the outersurface of collar 174. Spring 186 is compressed between guide ring 184and a support structure 188 that extends from central bore 182. In theexemplary embodiment, support structure 188 takes the form of a rigidring within a central aperture sized to fit around collar 174 whileretaining spring 184. Alternatively, support structure 188 may take anyother form including, for example, spring-loaded structures which may beretracted at least partially within the walls of central bore 182.

[0080] During normal operation of router 10, spring 186 maintains collar174 and spindle assembly 160 in its nominal or fully extended positionshown in FIG. 14. However, upon application of an axial force on spindleassembly 160 that is greater than, and opposite to, the force exerted byspring 186 (i.e., a retracting force), the collar and spindle assemblywill retract at least partially into housing 84 as can be seen in FIGS.15 and 16. The amount of retraction will be determined by the relativesizes and configurations of retractable spindle assembly 160,retractable bearing assembly 172, and coupling mechanism 164. In someembodiments, it may be desirable to retract router bit 98, or at leastthe cutting portion of the router bit, above support plate 94. Whererouter 10 is mounted to the underside of a router table, it may bedesirable to retract the router bit below the table. In any event, oncethe retracting force is removed from the spindle assembly, the urging ofspring 186 moves collar 174 and spindle assembly 160 back toward thefully extended position. While one exemplary configuration ofretractable bearing assembly 172 has been described above, it will beappreciated by those of skill in the art that many variations,modifications and alternative configurations may be used.

[0081] In response to detection of a dangerous condition by thedetection subsystem, reaction subsystem 24 is configured to cause aretracting force to be applied to retractable spindle assembly 160. Inthe exemplary embodiments depicted in FIGS. 14-17, the reactionsubsystem is configured to engage the spindle assembly and utilize therotational energy of the spindle assembly to create a retracting forceon the spindle assembly. However, it will be appreciated by those ofskill in the art that reaction subsystem 24 may be configured to causethe retracting force in any of a variety of different ways and that thedepicted embodiments are just a few examples of the many suitableconfigurations of reaction subsystem 24.

[0082] Exemplary reaction subsystem 24 includes a spindle engagementmember 190 adapted to engage a portion of spindle assembly 160 and urgethe spindle assembly to retract. Although not required, exemplaryspindle engagement member 190 is mounted in a removable cartridge 80attached to router housing 84 and/or base assembly 90. Retractablespindle assembly 160 includes an engagement structure 192 opposite end168. When spindle assembly 160 is in the fully extended positionengagement structure 192 is positioned adjacent spindle engagementmember 190. The engagement structure is formed to define one or moreguide structures 194 that project outward from the engagement structure.Alternatively, guide structures 194 may be formed as channels in theengagement structure as illustrated in FIG. 17. Exemplary guidestructures 194 extend around exemplary engagement structure 192 in agenerally helical pattern. The leading edges (as determined by thedirection of spindle rotation) of guide structures 194 are angled inwardtoward housing 84, while the trailing edges are angled outward from therouter housing.

[0083] Spindle engagement member 190 is configured to move from anunactuated or cocked position spaced apart from engagement structure 192as shown in FIG. 14, to an actuated position in contact with the side ofthe engagement structure shown in FIGS. 15 and 16. As the spindleassembly continues to rotate, one of the guide structures 194 willrotate into contact against the spindle engagement member. Therotational energy of the spindle assembly causes the guide structure toride along the spindle engagement member, thereby pushing the spindleassembly toward router housing 84 as can be seen in the simulatedtime-lapse illustrations of FIGS. 15 and 16. When the trailing edge ofthe guide structure rotates past the engagement member, the spindleengagement member moves further toward the spindle assembly to extendover the edge of the engagement structure and lock the spindle assemblyin a fully retracted position as shown in FIG. 16. Once spindleengagement member 190 locks into place over the edge of engagementstructure 192, spindle assembly 160 will remain in the fully retractedposition until the spindle engagement member is moved back away from theengagement structure to release the engagement structure and allow thespindle assembly to move out of the housing to a fully extended positionunder the urging of spring 186. Alternatively, cartridge 80 may beremoved to release the spindle assembly.

[0084] The speed with which spindle assembly 160 retracts away from theuser will be determined by the rotational speed of the spindle assemblyand the pitch of guide structures 194. For example, if the axial lengthof engagement structure 192 is 1-inch and an individual guide structuretravels the axial length over one circumference (i.e., a pitch of 1-inchper revolution), then a spindle assembly having a rotation speed of20,000-rpm will retract at a speed of approximately 28 ft/sec (i.e.,full retraction of 1-inch in approximately 3 msec). Since a retractionspeed of 28 ft/sec is substantially faster that the speed at which ahand or other portion of a user's body would ordinarily approach therouter bit, injury to the user would be minimized. Alternatively, otherguide structure pitches and spindle assembly speeds may be used.

[0085] As described above, reaction subsystem 24 engages the spindleassembly and converts at least a portion of the rotational energy orangular momentum of the spindle assembly into a retraction force on thespindle assembly. In other words, the spindle assembly isself-retracting upon engagement of spindle engagement member 190. Asdescribed above, the retraction of the spindle assembly also causesshaft 162 to uncouple from the spindle assembly, thereby allowing thespindle assembly and router bit to stop spinning. Typically, the angularmomentum of the spindle assembly will be sufficiently high that thespindle assembly will continue to spin for some finite amount of timeafter the spindle assembly is fully retracted. Alternatively, reactionsubsystem 24 may be configured to brake the rotation of the spindleassembly as in the exemplary embodiments described above. Additionally,spindle engagement member 190 may be configured to engage some brakingstructure (not shown) on the spindle assembly once the spindleengagement member extends over the edge of engagement structure 192.

[0086] It will be appreciated that spindle engagement member 190 may beconfigured in any of a variety of different ways which may vary with theconfiguration of spindle assembly 160 and engagement structure 192. Inthe exemplary embodiment depicted in FIGS. 14-16, spindle engagementmember 190 is generally cylindrically shaped and slidably disposed incircular bore 196 in cartridge 80. A biasing mechanism, such ascompression spring 198, is positioned to urge the spindle engagementmember from its unactuated position shown in FIG. 14 to its actuatedposition shown in FIGS. 15 and 16. The end of spindle engagement member190 opposite spring 198 is adapted to extend through a hole (not shown)in cartridge 80. Optionally the hole and/or other portions of thecartridge may be sealed against the entry of debris as described aboveand in the incorporated references.

[0087] Exemplary cartridge 80 also includes a restraining mechanismadapted to hold the spindle engagement member in its unactuated positionuntil a dangerous condition is detected. The exemplary restrainingmechanism includes a lever 200 pivotally coupled to the cartridgehousing. The short end of lever 200 extends into bore 196 to engagespindle engagement member 190. The long end of lever 200 is held by afusible member 70 anchored to a contact mount 72 such as describedabove. The contact mount forms part of a firing subsystem that alsoincludes a charge storage device such as capacitor 202. Upon detectionof a dangerous condition by the detection subsystem, the controlsubsystem controls the firing subsystem to discharge capacitor 202through contact mount 72, thereby melting fusible member 70 andreleasing lever 200. The lever is then free to pivot relative to thecartridge, allowing spindle engagement member 190 to move into contactwith engagement structure 192, as shown in FIGS. 15 and 16. Uponactuation of spindle engagement member 190, the expended cartridge 80 isreplaced with a new cartridge to return router 10 to operation. Variousalternative configurations of suitable cartridges and firing subsystemsare described in the incorporated references.

[0088] In the exemplary embodiments described above and depicted inFIGS. 14-17, reaction subsystem 24 was configured to use at least aportion of the angular momentum or rotational energy of the spindleassembly to generate a retraction force on the spindle assembly. It willbe appreciated however, that the reaction subsystem may alternatively beconfigured to generate a retraction force in other ways. For example,FIGS. 18-21 illustrate another exemplary embodiment in which reactionsubsystem 24 is configured to generate a retraction force independent ofthe energy or movement of the spindle assembly.

[0089] As can be seen in FIGS. 18-21, reaction subsystem 24 includes agenerally annular cartridge 80 adapted to fit around spindle assembly160 and to engage router housing 84 generally concentric with thespindle assembly. Retractable bearing assembly 172 includes a collar 204adapted to hold bearings 176, and having a generally annular recess 206adapted to receive cartridge 80. Collar 204 is adapted to slide within acentral bore 182 of housing 84. During normal operation, bearingassembly 172 is held in its fully extended (i.e., unretracted) positionshown in FIG. 18 by one or more springs 208 or other suitable biasingmechanisms. In the exemplary embodiment, springs 208 are disposed inchannels 210 formed in housing 84. Retractable bearing assembly 172includes one or more support members 212 which extend at least partiallyinto channels 210 and are engaged by springs 208 to maintain the bearingassembly under a constant bias toward the fully extended position.

[0090] When a retraction force is applied to bearing assembly 172 thatis greater than the force applied by springs 208, bearing assembly 172and spindle assembly 160 will retract at least partially away from theuser and into the router housing, as illustrated in FIG. 19. The amountof retraction will vary depending on the relative sizes andconfigurations of spindle assembly 160, coupling mechanism 164, centralbore 182, channels 210, support members 212, etc. In some embodiments,it may be desirable to retract router bit 98 (or at least the cuttingedges of the router bit) above support plate 94. In any event, uponremoval of the retraction force, bearing assembly 172 and spindleassembly 160 will return to the fully extended position under the urgingof springs 208.

[0091] Exemplary reaction subsystem 24 generates a retraction force onbearing assembly 172 through a biasing mechanism in cartridge 80. Theexemplary biasing mechanism has stored energy which is releasable upondetection of a dangerous condition by the detection system (not shown).It will be appreciated that reaction subsystem 24 may employ varioustypes of stored energy such as mechanical energy, chemical energy (e.g.,explosive), pressurized gas, etc. Alternatively, other types of biasingmechanisms may be used.

[0092] In the exemplary embodiment, the reaction subsystem storesmechanical energy in the form of a compression spring 214. Cartridge 80includes a base portion 216 and a releasable portion 218 releasablycoupled to the base portion. When coupled together, base portion 216 andreleasable portion 218 form an annular cavity adapted to hold spring 214in compression. During normal operation, base portion 216 and releasableportion 218 are held together by a restraining mechanism in the form ofone or more tabs 220 that extend from the base portion to grip thereleasable portion. Exemplary tabs 220 include a ridge structure 222adapted to grip a corresponding recess 224 of releasable portion 218.The ridge structures of tabs 220 are held tightly against recess 224 bya fusible member 70. Tabs 220 are somewhat flexible such that whenfusible member 70 is melted, the tabs will flex outward sufficiently toslide out of recess 224, thereby allowing releasable portion 218 to moveunder the urging of spring 214 as illustrated in FIG. 19. Spring 214 isadapted to exert a force on releasable portion 218 and bearing assembly172 that is substantially greater than the force exerted by springs 208,thereby causing the bearing assembly and spindle assembly to retractaway from the user when the fusible member is melted. Once the fusiblemember has been melted and the spindle assembly has retracted, the usedcartridge may be replaced by a new cartridge to return router 10 tooperation. Cartridge 80 may be coupled to housing 84 by any suitablemeans such as one or more bolts, etc.

[0093] As best seen in FIG. 20, fusible member 70 is positioned incontact with one or more electrodes 226 connected to a firing subsystem76 such as described above and in the incorporated references. Upondetection of a dangerous condition by the detection subsystem, firingsubsystem 76 supplies a surge of current across electrodes 226 to meltfusible member 70. In the exemplary embodiment, firing subsystem 76 isdisposed in a sub-housing 228 formed on or coupled to base portion 216.Sub-housing 228 includes one or more plugs or connectors 230 extendingfrom firing subsystem 76. Sub-housing 228 thus functions similar to anelectrical plug and is adapted to fit within a corresponding socket (notshown) in router housing 84. When properly coupled to the routerhousing, connectors 230 contact corresponding connectors within therouter housing to couple firing subsystem 76 to the control subsystem(not shown). Alternatively, one or more additional components of safetysystem 18 (including the control subsystem) may be mounted in cartridge80.

[0094] It will be appreciated that the speed with which spindle assembly160 retracts will vary depending on the force exerted by springs 208,the retraction force exerted by reaction subsystem 24, and the mass ofspindle assembly 160 and bearing assembly 172. In some embodiments itmay be desirable to select springs 208 and spring 214 to achieve a fullretraction in approximately 10-msec or less, and preferably inapproximately 5-msec or less. However, other retraction speeds may alsobe suitable depending on the particular application.

[0095] As described herein, safety system 18 provides an improved,active system for preventing or minimizing injuries from woodworkingmachines such as routers, etc. While several exemplary embodiments ofsafety system 18 are described above, the particular embodiments thathave been described serve to illustrate that many differentmodifications and alterations are possible within the scope of theinvention. It will be appreciated by those of skill in the art thatsafety system 18 may be adapted for use on a variety of other types ofwoodworking machines in addition to routers. Several examples of suchother machines, as well as further detailed descriptions of alternativesafety systems adaptable for use on routers may be found in thereferences incorporated above, as well as in the following references,the disclosures of which are herein incorporated by reference: PCTPatent Application Serial No. PCT/US00/26812, filed Sep. 29, 2000; U.S.patent application Ser. No. 09/929,221, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,226, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,227, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,234, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,235, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,236, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,237, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,238, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,240, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,241, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,242, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,244, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,425, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/929,426, filed Aug. 13, 2001; U.S. patentapplication Ser. No. 09/676,190, filed Sep. 29, 2000; U.S. ProvisionalPatent Application Serial No. 60/312,141, filed Aug. 13, 2001; U.S.Provisional Patent Application Serial No. 60/308,492, filed Jul. 27,2001; U.S. Provisional Patent Application Serial No. 60/307,756, filedJul. 25, 2001; U.S. Provisional Patent Application Serial No.60/306,202, filed Jul. 18, 2001; U.S. Provisional Patent ApplicationSerial No. 60/292,100, filed May 17, 2001; U.S. Provisional PatentApplication Serial No. 60/292,081, filed May 17, 2001; U.S. ProvisionalPatent Application Serial No. 60/279,313, filed Mar. 27, 2001; U.S.Provisional Patent Application Serial No. 60/275,595, filed Mar. 13,2001; U.S. Provisional Patent Application Serial No. 60/275,594, filedMar. 13, 2001; U.S. Provisional Patent Application Serial No.60/273,902, filed Mar. 6, 2001; U.S. Provisional Patent ApplicationSerial No. 60/273,178, filed Mar. 2, 2001; U.S. Provisional PatentApplication Serial No. 60/273,177, filed Mar. 2, 2001; U.S. ProvisionalPatent Application Serial No. 60/270,942, filed Feb. 22, 2001; U.S.Provisional Patent Application Serial No. 60/270,941, filed Feb. 22,2001; U.S. Provisional Patent Application Serial No. 60/233,459, filedSep. 18, 2000; U.S. Provisional Patent Application Serial No.60/225,210, filed Aug. 14, 2000; U.S. Provisional Patent ApplicationSerial No. 60/225,058, filed Aug. 14, 2000; U.S. Provisional PatentApplication Serial No. 60/225,057, filed Aug. 14, 2000; U.S. ProvisionalPatent Application Serial No. 60/182,866, filed Feb. 16, 2000; U.S.Provisional Patent Application Serial No. 60/157,340, filed Oct. 1,1999; and U.S. Pat. No. 4,267,914, issued May 19, 1981 to Saar.

[0096] It is believed that the disclosure set forth above encompassesmultiple distinct inventions with independent utility. While each ofthese inventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

[0097] It is believed that the following claims particularly point outcertain combinations and sub-combinations that are directed to one ofthe disclosed inventions and are novel and non-obvious. Inventionsembodied in other combinations and sub-combinations of features,functions, elements and/or properties may be claimed through amendmentof the present claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

We claim:
 1. A router for cutting workpieces with one or more routerbits, the router comprising: an operative structure configured tosupport a router bit in a nominal operating position to cut workpieces;a motor assembly coupled to rotate at least a portion of the operativestructure; and a safety system including a detection subsystemconfigured to detect one or more dangerous conditions between a personand a router bit supported by the operative structure, and a reactionsubsystem configured to retract the router bit at least partially awayfrom the nominal operating position if one or more dangerous conditionsare detected by the detection subsystem.
 2. The router of claim 1, wherethe reaction subsystem is configured to engage and stop the rotation ofat least a portion of the operative structure if one or more dangerousconditions are detected by the detection subsystem.
 3. The router ofclaim 1, where the reaction subsystem is configured to retract therouter bit at least partially away from the nominal operating positionwithin approximately 10 milliseconds after one or more dangerousconditions are detected by the detection subsystem.
 4. The router ofclaim 1, where the portion of the operative structure has rotationalenergy when rotating, and where the reaction subsystem is configured toutilize at least a portion of the rotational energy of the operativestructure to retract the router bit.
 5. The router of claim 1, where theoperative structure includes a rotatable shaft coupled to the motorassembly, a chuck configured to support a router bit, and a releasablecoupling configured to rotationally couple the chuck to the shaft, andwhere the releasable coupling is configured to rotationally uncouple thechuck from the shaft when the reaction subsystem retracts the router bitat least partially away from the nominal operating position.
 6. Therouter of claim 1, where the operative structure includes a retractablespindle assembly configured to support a router bit in the nominaloperating position, and where the retractable spindle assembly isselectively movable in a direction away from the nominal operatingposition, and where the reaction subsystem is configured to apply aretracting force on the retractable spindle assembly in a direction awayfrom the nominal operating position if one or more dangerous conditionsare detected by the detection subsystem.
 7. The router of claim 6, wherethe motor assembly is coupled to rotate the retractable spindle assemblyduring operation, where the retractable spindle assembly has rotationalenergy when rotating, and where the reaction subsystem is configured toconvert at least a portion of the rotational energy of the retractablespindle assembly into the retracting force on the retractable spindleassembly if one or more dangerous conditions are detected by thedetection subsystem.
 8. The router of claim 7, where the reactionsubsystem includes a spindle engagement member configured to selectivelyengage a portion of the retractable spindle assembly and urge theretractable spindle assembly in a direction away from the nominaloperating position.
 9. The router of claim 8, further comprising ahousing configured to at least partially enclose the motor assembly andthe operative structure, and a disposable cartridge assembly removablymounted to the housing, and where the spindle engagement member ismounted in the cartridge assembly.
 10. The router of claim 1, furthercomprising a housing configured to at least partially enclose the motorassembly and the operative structure, and a disposable cartridgeassembly removably mounted to the housing, and where at least a portionof the reaction subsystem is mounted in the disposable cartridgeassembly.
 11. For use with a router adapted to rotationally drive arouter bit, a method for minimizing injury from a router bit coupled tothe router, the method comprising: detecting accidental contact betweena person and the router bit; and at least partially retracting therouter bit away from the person in the event accidental contact betweenthe person and the router bit is detected.
 12. The method of claim 11,where the step of retracting includes at least partially retracting therouter bit away from the person within 10 milliseconds after theaccidental contact between a person and the router bit is detected. 13.The method of claim B, further comprising the step of stopping therotation of the router bit in the event accidental contact between theperson and the router bit is detected.
 14. The method of claim 11, wherethe step of detecting includes the steps of: applying an electrical tothe router bit, and monitoring the electrical signal on the router bitchanges indicative of accidental contact between a person and the routerbit.
 15. The method of claim 11, where the router includes rotatableoperative structure configured to support a router bit, where theoperative structure has angular momentum when rotating, and where thestep of retracting includes converting at least a portion of the angularmomentum of the operative structure into a retraction force on theoperative structure in a direction away from the person.
 16. A routercomprising: means for rotationally driving a router bit; means fordetecting accidental contact between a person and the router bit; andmeans for at least partially retracting the router bit away from theperson in the event accidental contact between the person and the routerbit is detected.
 17. The router of claim 16, further comprising meansfor stopping the rotation of the router bit in the event accidentalcontact between the person and the router bit is detected.
 18. Therouter of claim 16, where the means for retracting includes means forretracting the router bit away from the person within 10 millisecondsafter accidental contact between the person and the router bit isdetected.
 19. The router of claim 16, further comprising biasing meansfor maintaining the router bit in a nominal operating position untilaccidental contact between the person and the router bit is detected.20. The router of claim 19, where the biasing means include means forreleasably maintaining the router bit in a fully retracted positionafter contact between the person and the router bit is detected.